Quantum ESPRESSO Input

The input to the QuantumESPRESSO engine has a similar structure as the input to the pw.x executable, with some exceptions.

Note

In the input file there are two System blocks:

  • The AMS driver System block contains the atomic species, atomic positions, atomic masses (isotopes), and lattice vectors, just like for any other AMS calculation. On each atom line you can also specify for example QE.label=Fe1 (max 3 characters) to set the internal QE atom type for that atom. See the Examples.

  • The QuantumESPRESSO Engine System block contains keywords from the &SYSTEM namelist in the pw.x input file. For example, ecutwfc to set the plane-wave energy cutoff, as well as many other input options for magnetization, occupations, dispersion corrections, etc. This block is described in detail below.

Pseudopotentials

A library of pseudopotentials is included with the AMS Quantum ESPRESSO package. Simply specify the family and the functional in the input and the corresponding pseudopotential files will be used.

The pseudopotentials will also determine the exchange-correlation functional used, unless you set manually set the DFT functional (input_dft) option.

Important

Use an energy cutoff that is large enough for your selected pseudopotentials!

Pseudopotentials
   Directory string
   Family [Dojo | GBRV | pslibrary-PAW | pslibrary-US | SG15 | SSSP-Efficiency | SSSP-Precision]
   Files
      Label string
      Path string
   End
   FullyRelativistic Yes/No
   Functional [BLYP | LDA | PBE | PBEsol | PW91]
End
Pseudopotentials
Type:

Block

Description:

Selects the pseudopotential to use for the atomic species.

Directory
Type:

String

Description:

This key is mutually exclusive with the Family and Files keywords. This key specifies a directory containing label.upf files. Example: System Atoms H 0 0 0 H 0 0 1 QE.Label=H1 H 0 0 2 QE.Label=H2 C 0 0 3 QE.Label=C1 End End This will look for the files H.upf, H1.upf, H2.upf, C1.upf. If H1.upf does not exist, H.upf will be used. If H2.upf does not exist, H.upf will be used. If C1.upf does not exist, C.upf will be used.

Family
Type:

Multiple Choice

Default value:

SSSP-Efficiency

Options:

[Dojo, GBRV, pslibrary-PAW, pslibrary-US, SG15, SSSP-Efficiency, SSSP-Precision]

GUI name:

Pseudopotential family

Description:

The pseudopotential family to use. Mutually exclusive with the Files and Directory keywords.

Files
Type:

Block

Recurring:

True

Description:

Selects the pseudopotentials to use for each atomic species. This key is mutually exclusive with the Family and Directory keywords.

Label
Type:

String

Description:

Label for an atom corresponding to the QE.Label, or to the element symbol if QE.Label is not set.

Path
Type:

String

Description:

Path to a .upf file to use as pseudopotential. Relative paths are relative to root of the pseudopotential library shipped with AMS. Prefix a path with ‘./’ to make it relative to the starting directory of your job.

FullyRelativistic
Type:

Bool

Default value:

No

GUI name:

Pseudopotential fully relativistic

Description:

Whether to use fully relativistic pseudopotentials (required for spin-orbit calculations).

Functional
Type:

Multiple Choice

Default value:

PBE

Options:

[BLYP, LDA, PBE, PBEsol, PW91]

GUI name:

Pseudopotential functional

Description:

Exchange-correlation functional that was used to generate the pseudopotential. Not all choices are valid for all pseudopotential families. This functional will also be used for the calculation, unless the input_dft option is set.

K-space and k-point sampling

The K_Points block corresponds to the K_POINTS card in the pw.x input.

Gamma-point (Γ-point) sampling (fast implementation, not compatible with all calculation types or postprocessing programs):

Engine QuantumEspresso
    K_Points gamma
    End
EndEngine

Gamma-point (Γ-point) sampling (slower implementation):

Engine QuantumEspresso
    K_Points automatic
        1 1 1 0 0 0
    End
EndEngine

Monkhorst-Pack 6 x 6 x 4 grid, shifted:

Engine QuantumEspresso
   K_Points automatic
     6 6 4 1 1 1
   End
EndEngine

Monkhorst-Pack 6 x 6 x 4 grid, unshifted:

Engine QuantumEspresso
   K_Points automatic
     6 6 4 0 0 0
   End
EndEngine

The output contains details about the generated k-point grid. For further information, see the pw.x documentation.

For DOS and band structure calculations, the main K_Points block specifies the k-points used during the self-consistent-field (SCF). The DOS and band structure sections for how to specify a different k-space sampling for the non-self-consistent parts of DOS and band structure calculations.

K_Points
Type:

Non-standard block

Description:

Specify the k-points to use. Available header values are: tpiba, automatic, crystal, gamma, tpiba_b, crystal_b, tpiba_c, crystal_c, and ams_kpath. See the examples and QE documentation for details. If omitted, only gamma is used. For most cases, automatic (which generates a Monkhorst-Pack grid) is recommended. Note: Gamma-point calculations are significantly faster using gamma than automatic, but may not be possible to use for all types of calculations or postprocessing programs.

Control block: dipole/electric field

See also

Dipole/charge corrections

Control
   dipfield Yes/No
   lelfield Yes/No
   tefield Yes/No
End
Control
Type:

Block

Description:

Keywords from the &CONTROL namelist in the QuantumEspresso input file.

dipfield
Type:

Bool

Default value:

No

GUI name:

Dipole field

Description:

If True (and tefield is True) a dipole correction is also added to the bare ionic potential - implements the recipe of L. Bengtsson, PRB 59, 12301 (1999). See keywords edir, emaxpos, eopreg for the form of the correction. Must be used ONLY in a slab geometry, for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE.

lelfield
Type:

Bool

Default value:

No

GUI name:

Homogeneous E-field

Description:

If True a homogeneous finite electric field described through the modern theory of the polarization is applied. This is different from setting tefield to True!

tefield
Type:

Bool

Default value:

No

GUI name:

Saw-like E-field

Description:

If True a saw-like potential simulating an electric field is added to the bare ionic potential. See keywords edir, eamp, emaxpos, eopreg for the form and size of the added potential.

Electrons block: SCF convergence

Electrons
   conv_thr float
   diagonalization [Davidson | ConjugateGradient | PPCG | ParO | RMM-Davidson | RMM-ParO]
   electron_maxstep integer
   mixing_beta float
   mixing_mode [Plain | Thomas-Fermi | Local-Thomas-Fermi]
   mixing_ndim integer
End
Electrons
Type:

Block

Description:

Keywords from the &ELECTRONS namelist in the QuantumEspresso input file.

conv_thr
Type:

Float

Default value:

1e-06

Unit:

Rydberg

GUI name:

Convergence threshold

Description:

Convergence threshold for selfconsistency: estimated energy error < conv_thr. Note that conv_thr is extensive, like the total energy.

diagonalization
Type:

Multiple Choice

Default value:

Davidson

Options:

[Davidson, ConjugateGradient, PPCG, ParO, RMM-Davidson, RMM-ParO]

GUI name:

Diagonalization

Description:

Available options are: • Davidson: iterative diagonalization with overlap matrix. Fast, may in some rare cases fail. • ConjugateGradient: Conjugate-gradient-like band-by-band diagonalization. MUCH slower than Davidson but uses less memory and is (a little bit) more robust. • PPCG: PPCG iterative diagonalization • ParO: ParO iterative diagonalization • RMM-Davidson & RMM-ParO: RMM-DIIS iterative diagonalization. To stabilize the SCF loop RMM-DIIS is alternated with calls to Davidson or ParO solvers.

electron_maxstep
Type:

Integer

Default value:

100

GUI name:

Maximum # SCF iterations

Description:

Maximum number of iterations in a SCF step.

mixing_beta
Type:

Float

Default value:

0.3

GUI name:

Beta

Description:

Mixing factor for self-consistency. Note: the default value in the AMS interface (0.3) is smaller than the default value in pw.x (0.7)

mixing_mode
Type:

Multiple Choice

Default value:

Plain

Options:

[Plain, Thomas-Fermi, Local-Thomas-Fermi]

GUI name:

Mixing mode

Description:

Available options are: • Plain: charge density Broyden mixing • Thomas-Fermi: as above, with simple Thomas-Fermi screening (for highly homogeneous systems) • Local-Thomas-Fermi: as above, with local-density-dependent TF screening (for highly inhomogeneous systems)

mixing_ndim
Type:

Integer

Default value:

8

GUI name:

Dimension

Description:

Number of iterations used in mixing scheme. If you are tight with memory, you may reduce it to 4 or so.

System block (in the QuantumESPRESSO engine)

Overview:

System
   assume_isolated [Auto | None | Martyna-Tuckerman | ESM | 2D]
   degauss float
   dftd3_threebody Yes/No
   dftd3_version [2 | 3 | 4 | 5 | 6]
   eamp float
   ecutfock float
   ecutrho float
   ecutvcut float
   ecutwfc float
   edir [1 | 2 | 3]
   emaxpos float
   eopreg float
   exx_fraction float
   exxdiv_treatment [gygi-baldereschi | vcut_spherical | vcut_ws | none]
   input_dft string
   lspinorb Yes/No
   nbnd integer
   nqx1 integer
   nqx2 integer
   nqx3 integer
   nr1 integer
   nr1s integer
   nr2 integer
   nr2s integer
   nr3 integer
   nr3s integer
   nspin [None | Collinear | Non-Collinear]
   occupations [Smearing | Tetrahedra | Tetrahedra_lin | Tetrahedra_opt | Fixed]
   screening_parameter float
   smearing [Gaussian | Methfessel-Paxton | Marzari-Vanderbilt | Fermi-Dirac]
   starting_magnetization
      Label string
      Value float
   End
   tot_magnetization float
   vdw_corr [None | Grimme-D2 | Grimme-D3 | TS | MBD | XDM]
   x_gamma_extrapolation Yes/No
   xdm_a1 float
   xdm_a2 float
End

Cutoffs

System
   ecutrho float
   ecutwfc float
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

ecutrho
Type:

Float

Unit:

Rydberg

GUI name:

Charge density cutoff

Description:

Kinetic energy cutoff for charge density and potential. If this key is not specified and the Pseudopotential%Family recommends a ratio of ecutrho to ecutwfc, this recommended ratio will be used. If there is no recommended ratio, the default value is 4 x ecutwfc. For norm-conserving pseudopotential you should stick to the default value, you can reduce it by a little but it will introduce noise especially on forces and stress. If there are ultrasoft PP, a larger value than the default is often desirable (ecutrho = 8 to 12 times ecutwfc, typically). PAW datasets can often be used at 4 x ecutwfc, but it depends on the shape of augmentation charge: testing is mandatory. The use of gradient-corrected functional, especially in cells with vacuum, or for pseudopotential without non-linear core correction, usually requires an higher values of ecutrho to be accurately converged.

ecutwfc
Type:

Float

Default value:

40.0

Unit:

Rydberg

GUI name:

Wavefunction energy cutoff

Description:

Kinetic energy cutoff for wavefunctions.

See also

Exact exchange (EXX)

Number of bands (nbnd)

System
   nbnd integer
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

nbnd
Type:

Integer

GUI name:

Number of bands

Description:

Number of electronic states (bands) to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled. Default: For an insulator, nbnd = number of valence bands (nbnd = # of electrons /2); for a metal, 20% more (minimum 4 more)

Fractional occupation, smearing

System
   degauss float
   occupations [Smearing | Tetrahedra | Tetrahedra_lin | Tetrahedra_opt | Fixed]
   smearing [Gaussian | Methfessel-Paxton | Marzari-Vanderbilt | Fermi-Dirac]
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

degauss
Type:

Float

Default value:

0.0

Unit:

Rydberg

GUI name:

Smearing width

Description:

Value of the gaussian spreading for Brillouin-zone integration in metals.

occupations
Type:

Multiple Choice

Default value:

Fixed

Options:

[Smearing, Tetrahedra, Tetrahedra_lin, Tetrahedra_opt, Fixed]

GUI name:

Occupations

Description:

Available options are: • Smearing: gaussian smearing for metals; see keywords smearing and degauss • Tetrahedra: Tetrahedron method, Bloechl’s version: P.E. Bloechl, PRB 49, 16223 (1994). Requires uniform grid of k-points, to be automatically generated (see block K_Points). Well suited for calculation of DOS, less so (because not variational) for force/optimization/dynamics calculations. • Tetrahedra_lin: Original linear tetrahedron method. To be used only as a reference; the optimized tetrahedron method is more efficient. • Tetrahedra_opt: optimized tetrahedron method, see M. Kawamura, PRB 89, 094515 (2014). Can be used for phonon calculations as well. • Fixed: for insulators with a gap.

smearing
Type:

Multiple Choice

Default value:

Gaussian

Options:

[Gaussian, Methfessel-Paxton, Marzari-Vanderbilt, Fermi-Dirac]

GUI name:

Smearing

Description:

Available options are: • Gaussian: ordinary Gaussian spreading • Methfessel-Paxton: first-order spreading (see PRB 40, 3616 (1989)) • Marzari-Vanderbilt: cold smearing (see PRL 82, 3296 (1999)) • Fermi-Dirac: smearing with Fermi-Dirac function

Magnetization, spin, spin-orbit

System
   lspinorb Yes/No
   nspin [None | Collinear | Non-Collinear]
   starting_magnetization
      Label string
      Value float
   End
   tot_magnetization float
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

lspinorb
Type:

Bool

GUI name:

Spin-orbit

Description:

if .TRUE. the noncollinear code can use a pseudopotential with spin-orbit.

nspin
Type:

Multiple Choice

Default value:

None

Options:

[None, Collinear, Non-Collinear]

GUI name:

Magnetization

Description:

Available options are: • None: not spin-polarized • Collinear: LSDA with magnetization along z-axis • Non-Collinear: any magnetization (equivalent to setting the noncolin key to True)

starting_magnetization
Type:

Block

Recurring:

True

Description:

Starting spin polarization for an atomic type in a spin polarized (LSDA or noncollinear/spin-orbit) calculation. Allowed values range between -1 (all spins down for the valence electrons of atom type ‘i’) to 1 (all spins up). If you expect a nonzero magnetization in your ground state, you MUST either specify a nonzero value for at least one atomic type, or constrain the magnetization using keyword tot_magnetization for LSDA, constrained_magnetization for noncollinear/spin-orbit calculations. If you don’t, you will get a nonmagnetic (zero magnetization) state. In order to perform LSDA calculations for an antiferromagnetic state, define two different atomic species corresponding to sublattices of the same atomic type. Note: If you fix the magnetization with tot_magnetization, do not specify starting_magnetization. Note: In the noncollinear/spin-orbit case, starting with zero starting_magnetization on all atoms imposes time reversal symmetry. The magnetization is never calculated and is set to zero.

Label
Type:

String

Description:

Label for an atom corresponding to the QE.Label, or to the element symbol if QE.Label is not set.

Value
Type:

Float

Description:

Starting magnetization value.

tot_magnetization
Type:

Float

GUI name:

Fix total magnetization

Description:

Total majority spin charge minus minority spin charge. Used to impose a specific total electronic magnetization. If unspecified then tot_magnetization variable is ignored and the amount of electronic magnetization is determined during the self-consistent cycle.

Dispersion corrections

Tip

You can access Grimme’s D4 dispersion through an AMS engine addon.

System
   vdw_corr [None | Grimme-D2 | Grimme-D3 | TS | MBD | XDM]
   dftd3_version [2 | 3 | 4 | 5 | 6]
   dftd3_threebody Yes/No
   xdm_a1 float
   xdm_a2 float
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

vdw_corr
Type:

Multiple Choice

Default value:

None

Options:

[None, Grimme-D2, Grimme-D3, TS, MBD, XDM]

GUI name:

Dispersion correction

Description:

Type of Van der Waals correction. Allowed values: • Grimme-D2: Semiempirical Grimme’s DFT-D2, see S. Grimme, J. Comp. Chem. 27, 1787 (2006) [doi:10.1002/jcc.20495], and V. Barone et al., J. Comp. Chem. 30, 934 (2009) [doi:10.1002/jcc.21112]. • Grimme-D3: Semiempirical Grimme’s DFT-D3, see S. Grimme et al, J. Chem. Phys 132, 154104 (2010) [doi:10.1063/1.3382344]. • TS: Tkatchenko-Scheffler dispersion corrections with first-principle derived C6 coefficients, see A. Tkatchenko and M. Scheffler, PRL 102, 073005 (2009). • MBD: Many-body dispersion (MBD) correction to long-range interactions, see A. Ambrosetti, A. M. Reilly, R. A. DiStasio, A. Tkatchenko, J. Chem. Phys. 140 18A508 (2014). • XDM: Exchange-hole dipole-moment model, see A. D. Becke et al., J. Chem. Phys. 127, 154108 (2007) [doi:10.1063/1.2795701], and A. Otero de la Roza et al., J. Chem. Phys. 136, 174109 (2012) [doi:10.1063/1.4705760]. Note that non-local functionals (eg vdw-DF) are NOT specified here but using the input_dft keyword.

dftd3_version
Type:

Multiple Choice

Default value:

3

Options:

[2, 3, 4, 5, 6]

GUI name:

Version

Description:

Version of Grimme implementation of Grimme-D3: • 2: Original Grimme-D2 parametrization • 3: Grimme-D3 (zero damping) • 4: Grimme-D3 (BJ damping) • 5: Grimme-D3M (zero damping) • 6: Grimme-D3M (BJ damping) • NOTE: not all functionals are parametrized.

dftd3_threebody
Type:

Bool

Default value:

Yes

GUI name:

Use three-body terms

Description:

Turn three-body terms in Grimme-D3 on. If False two-body contributions only are computed, using two-body parameters of Grimme-D3. If dftd3_version is set to 2, three-body contribution is always disabled.

xdm_a1
Type:

Float

Default value:

0.6836

GUI name:

a1

Description:

Damping function parameter a1 (adimensional). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM; A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013) [doi:10.1063/1.4705760]

xdm_a2
Type:

Float

Default value:

1.5045

Unit:

Angstrom

GUI name:

a2

Description:

Damping function parameter a2 (Angstrom). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM; A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013) [doi:10.1063/1.4705760]

Example values for xdm_a1 and xdm_a2 (source: postsg/xdm.param)

# quantum espresso, new version
functional       a1    a2(ang)  MAPD nset
b86bpbe (PAW)  0.6512  1.4633   11.8  49
pw86pbe (PAW)  0.6836  1.5045   11.7  49
blyp    (PAW)  0.4502  1.6210   14.8  49
pbe     (PAW)  0.3275  2.7673   14.4  49
b86bpbe (NC)   0.7767  1.0937   12.4  49
pw86pbe (NC)   0.7825  1.2077   12.6  49
blyp    (NC)   0.6349  1.0486   11.2  49
pbe     (NC)   0.4283  2.4690   15.2  49

# quantum espresso, new version, hybrids
functional           a1    a2(ang)  MAPD nset
hse         (PAW)  0.3799  2.5862   10.5  49
pbe0        (PAW)  0.4616  2.2913    7.9  49
b3lyp       (PAW)  0.6092  1.3452    8.5  49
b86bpbe 10% (PAW)  0.6470  1.4911   10.1  49
b86bpbe 20% (PAW)  0.6303  1.5579    8.8  49
b86bpbe 30% (PAW)  0.6134  1.6290    7.8  49
b86bpbe 40% (PAW)  0.5976  1.7000    7.1  49
b86bpbe 50% (PAW)  0.5826  1.7718    6.9  49
blyp 10%    (PAW)  0.5637  1.4443   10.0  49
blyp 20%    (PAW)  0.5663  1.5258    8.8  49
blyp 30%    (PAW)  0.5174  1.7808    8.5  49
blyp 40%    (PAW)  0.4195  2.1999    8.6  49
bhahlyp     (PAW)  0.2998  2.6953    9.3  49
b3lyp       (NC)   0.6070  1.3862    7.4  49
pbe0        (NC)   0.4590  2.3581   11.1  49
hse         (NC)   0.4206  2.4989   11.9  49
b86bpbe 10% (NC)   0.7272  1.2674   10.8  49
b86bpbe 20% (NC)   0.6898  1.4072    9.6  49
b86bpbe 25% (NC)   0.6754  1.4651    9.2  49
b86bpbe 30% (NC)   0.6627  1.5181    9.0  49
b86bpbe 40% (NC)   0.6465  1.5981    8.9  49
b86bpbe 50% (NC)   0.6434  1.6405    9.1  49
blyp 10%    (NC)   0.5967  1.3653    8.6  49
blyp 20%    (NC)   0.5315  1.6669    7.8  49
blyp 30%    (NC)   0.4398  2.0623    8.1  49
blyp 40%    (NC)   0.3375  2.5011    9.1  49
bhahlyp     (NC)   0.2292  2.9698   10.4  49

DFT functional (input_dft)

See also

Exact exchange (EXX)

System
   input_dft string
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

input_dft
Type:

String

GUI name:

Density functional

Description:

Exchange-correlation functional. Some valid values are • pbe • blyp • pbe0 • hse • revpbe • vdw-df-cx. See the documentation for more possible values. Overrides the value read from pseudopotential files.

Valid values for input_dft (source: Modules/funct.f90)

  ! ------------------------------------------------------------------------
  ! "dft" is the exchange-correlation functional label, as set by the user,
  ! using either set_dft_from_name or set_dft_from_indices. It can contain
  ! either the short names or a series of the keywords listed below.
  ! All operations on names are case-insensitive.
  !
  !           short name       complete name       Short description
  !              "pz"    = "sla+pz"            = Perdew-Zunger LDA
  !              "bp"    = "b88+p86"           = Becke-Perdew grad.corr.
  !              "pw91"  = "sla+pw+ggx+ggc"    = PW91 (aka GGA)
  !              "blyp"  = "sla+b88+lyp+blyp"  = BLYP
  !              "pbe"   = "sla+pw+pbx+pbc"    = PBE
  !              "revpbe"= "sla+pw+revx+pbc"   = revPBE (Zhang-Yang)
  !              "rpbe"  = "sla+pw+hhnx+pbc"   = RPBE (Hammer-Hansen-Norskov)
  !              "pw86pbe" = "sla+pw+pw86+pbc" = PW86 exchange + PBE correlation
  !              "b86bpbe" = "sla+pw+b86b+pbc" = B86b exchange + PBE correlation
  !              "pbesol"= "sla+pw+psx+psc"    = PBEsol
  !              "q2d"   = "sla+pw+q2dx+q2dc"  = PBEQ2D
  !              "hcth"  = "nox+noc+hcth+hcth" = HCTH/120
  !              "olyp"  = "nox+lyp+optx+blyp" = OLYP
  !              "wc"    = "sla+pw+wcx+pbc"    = Wu-Cohen
  !              "sogga" = "sla+pw+sox+pbec"   = SOGGA
  !              "optbk88"="sla+pw+obk8+p86"   = optB88
  !              "optb86b"="sla+pw+ob86+p86"   = optB86
  !              "ev93"  = "sla+pw+evx+nogc"   = Engel-Vosko

  !              "tpss"  = "sla+pw+tpss+tpss"  = TPSS Meta-GGA
  !              "m06l"  = "nox+noc+m6lx+m6lc" = M06L Meta-GGA
  !              "tb09"  = "sla+pw+tb09+tb09"  = TB09 Meta-GGA
  !              "pbe0"  = "pb0x+pw+pb0x+pbc"  = PBE0
  !              "b86bx" = "pb0x+pw+b86x+pbc"  = B86bPBE hybrid
  !              "bhahlyp"="pb0x+pw+b88x+blyp" = Becke half-and-half LYP
  !              "hse"   = "sla+pw+hse+pbc"    = Heyd-Scuseria-Ernzerhof (HSE 06, see note below)
  !              "b3lyp"                        = B3LYP
  !              "b3lyp-v1r"                    = B3LYP-VWN1-RPA
  !              "x3lyp"                        = X3LYP
  !              "vwn-rpa" = VWN LDA using vwn1-rpa parametrization
  !              "gaupbe"= "sla+pw+gaup+pbc"   = Gau-PBE (also "gaup")
  !
  !              "vdw-df"       ="sla+pw+revx+vdw1"      = vdW-DF1
  !              "vdw-df2"      ="sla+pw+rw86+vdw2"      = vdW-DF2
  !              "vdw-df-c09"   ="sla+pw+c09x+vdw1"      = vdW-DF-C09
  !              "vdw-df2-c09"  ="sla+pw+c09x+vdw2"      = vdW-DF2-C09
  !              "vdw-df-obk8"  ="sla+pw+obk8+vdw1"      = vdW-DF-obk8 (optB88-vdW)
  !              "vdw-df-ob86"  ="sla+pw+ob86+vdw1"      = vdW-DF-ob86 (optB86b-vdW)
  !              "vdw-df2-b86r" ="sla+pw+b86r+vdw2"      = vdW-DF2-B86R (rev-vdw-df2)
  !              "vdw-df-cx"    ="sla+pw+cx13+vdW1"      = vdW-DF-cx
  !              "vdw-df-cx0"   ="sla+pw+cx13+vdW1+HF/4" = vdW-DF-cx-0
  !              "vdw-df2-0"    ="sla+pw+rw86+vdw2+HF/4" = vdW-DF2-0
  !              "vdw-df2-br0"  ="sla+pw+b86r+vdW2+HF/4" = vdW-DF2-b86r-0
  !              "vdw-df-c090"  ="sla+pw+c09x+vdw1+HF/4" = vdW-DF-C09-0
  !              "vdw-df3-opt1" ="sla+pw+w31x+w31c"      = vdW-DF3-opt1
  !              "vdw-df3-opt2" ="sla+pw+w32x+w32c"      = vdW-DF3-opt2
  !              "vdw-df-C6"    ="sla+pw+b86r+wc6"       = vdW-DF-C6
  !              "rvv10" = "sla+pw+rw86+pbc+vv10"        = rVV10
  !
  ! Any nonconflicting combination of the following keywords is acceptable:
  !
  ! Exchange:    "nox"    none                           iexch=0
  !              "sla"    Slater (alpha=2/3)             iexch=1 (default)
  !              "sl1"    Slater (alpha=1.0)             iexch=2
  !              "rxc"    Relativistic Slater            iexch=3
  !              "oep"    Optimized Effective Potential  iexch=4
  !              "hf"     Hartree-Fock                   iexch=5
  !              "pb0x"   (Slater*0.75+HF*0.25)          iexch=6 for PBE0 and vdW-DF-cx0 and vdW-DF2-0 etc
  !              "b3lp"   B3LYP(Slater*0.80+HF*0.20)     iexch=7
  !              "kzk"    Finite-size corrections        iexch=8
  !              "x3lp"   X3LYP(Slater*0.782+HF*0.218)   iexch=9
  !              "kli"    KLI aproximation for exx       iexch=10
  !
  ! Correlation: "noc"    none                           icorr=0
  !              "pz"     Perdew-Zunger                  icorr=1 (default)
  !              "vwn"    Vosko-Wilk-Nusair              icorr=2
  !              "lyp"    Lee-Yang-Parr                  icorr=3
  !              "pw"     Perdew-Wang                    icorr=4
  !              "wig"    Wigner                         icorr=5
  !              "hl"     Hedin-Lunqvist                 icorr=6
  !              "obz"    Ortiz-Ballone form for PZ      icorr=7
  !              "obw"    Ortiz-Ballone form for PW      icorr=8
  !              "gl"     Gunnarson-Lunqvist             icorr=9
  !              "kzk"    Finite-size corrections        icorr=10
  !              "vwn-rpa" Vosko-Wilk-Nusair, alt param  icorr=11
  !              "b3lp"   B3LYP (0.19*vwn+0.81*lyp)      icorr=12
  !              "b3lpv1r"  B3LYP-VWN-1-RPA
  !                         (0.19*vwn_rpa+0.81*lyp)      icorr=13
  !              "x3lp"   X3LYP (0.129*vwn_rpa+0.871*lyp)icorr=14
  !
  ! Gradient Correction on Exchange:
  !              "nogx"   none                           igcx =0 (default)
  !              "b88"    Becke88 (beta=0.0042)          igcx =1
  !              "ggx"    Perdew-Wang 91                 igcx =2
  !              "pbx"    Perdew-Burke-Ernzenhof exch    igcx =3
  !              "revx"   revised PBE by Zhang-Yang      igcx =4
  !              "hcth"   Cambridge exch, Handy et al    igcx =5
  !              "optx"   Handy's exchange functional    igcx =6
  !              "pb0x"   PBE0 (PBE exchange*0.75)       igcx =8

  !              "b3lp"   B3LYP (Becke88*0.72)           igcx =9
  !              "psx"    PBEsol exchange                igcx =10
  !              "wcx"    Wu-Cohen                       igcx =11
  !              "hse"    HSE screened exchange          igcx =12
  !              "rw86"   revised PW86                   igcx =13
  !              "pbe"    same as PBX, back-comp.        igcx =14
  !              "c09x"   Cooper 09                      igcx =16
  !              "sox"    sogga                          igcx =17
  !              "q2dx"   Q2D exchange grad corr         igcx =19
  !              "gaup"   Gau-PBE hybrid exchange        igcx =20
  !              "pw86"   Perdew-Wang (1986) exchange    igcx =21
  !              "b86b"   Becke (1986) exchange          igcx =22
  !              "obk8"   optB88  exchange               igcx =23
  !              "ob86"   optB86b exchange               igcx =24
  !              "evx"    Engel-Vosko exchange           igcx =25
  !              "b86r"   revised Becke (b86b)           igcx =26
  !              "cx13"   consistent exchange            igcx =27
  !              "x3lp"   X3LYP (Becke88*0.542 +
  !                              Perdew-Wang91*0.167)    igcx =28
  !              "cx0"    vdW-DF-cx+HF/4 (cx13-0)        igcx =29
  !              "r860"   rPW86+HF/4 (rw86-0)            igcx =30 (for DF0)
  !              "cx0p"   vdW-DF-cx+HF/5 (cx13-0p)       igcx =31
  !              "ahcx"   vdW-DF-cx based analytic hole  igcx =32 ! Launched vdW-DF-ahcx - PH
  !              "ahf2"   vdW-DF2 based analytic hole    igcx =33 ! Defined vdw-DF2-AH at 0.20 - PH
  !              "ahpb"   PBE based analytic hole        igcx =34 ! PBE-AH (rHJS-PBE) at 0.20 - PH
  !              "ahps"   PBE-sol based analytic hole    igcx =35 ! PBESOL-AH (rHJS-PBEsol) at 0.20 - PH
  !              "cx14"   Exporations                    igcx =36 reserved PH
  !              "cx15"   Exporations                    igcx =37 reserved PH
  !              "br0"    vdW-DF2-b86r+HF/4 (b86r-0)     igcx =38
  !              "cx16"   Exporations                    igcx =39 reserved PH
  !              "c090"   vdW-DF-c09+HF/4 (c09-0)        igcx =40
  !              "b86x"   B86b exchange * 0.75           igcx =41
  !              "b88x"   B88 exchange * 0.50            igcx =42
  !              "beex"   BEE exchange                   igcx =43
  !              "hhnx"   Hammer-Hansen-Norskov          igcx =44
  !              "w31x"   vdW-DF3-opt1 exchange          igcx =45
  !              "w32x"   vdW-DF3-opt2 exchange          igcx =46
  !              "ahtr"   vdW-DF2-ahtr exchange          igcx =47 ! Test reserve called by vdW-DF2-ahtr - PH
  !              "ehpb"   HSE variant                    igcx =48 ! Reserved PH
  !              "hjpb"   HJS-type PBE cross check       igcx =49 ! Reserved PH
  !              "hjps"   HJS-type PBEsol crosscheck     igcx =50 ! Reserved PH
  !
  ! Gradient Correction on Correlation:
  !              "nogc"   none                           igcc =0 (default)
  !              "p86"    Perdew86                       igcc =1
  !              "ggc"    Perdew-Wang 91 corr.           igcc =2
  !              "blyp"   Lee-Yang-Parr                  igcc =3
  !              "pbc"    Perdew-Burke-Ernzenhof corr    igcc =4
  !              "hcth"   Cambridge corr, Handy et al    igcc =5
  !              "b3lp"   B3LYP (Lee-Yang-Parr*0.81)     igcc =7
  !              "psc"    PBEsol corr                    igcc =8
  !              "pbe"    same as PBX, back-comp.        igcc =9
  !              "q2dc"   Q2D correlation grad corr      igcc =12
  !              "x3lp"   X3LYP (Lee-Yang-Parr*0.871)    igcc =13
  !              "beec"   BEE correlation                igcc =14
  !
  ! Meta-GGA functionals
  !              "tpss"   TPSS Meta-GGA                  imeta=1
  !              "m6lx"   M06L Meta-GGA                  imeta=2
  !              "tb09"   TB09 Meta-GGA                  imeta=3
  !              "+meta"  activate MGGA even without MGGA-XC   imeta=4
  !              "scan"   SCAN Meta-GGA                  imeta=5
  !              "sca0"   SCAN0  Meta-GGA                imeta=6
  !              "r2scan" R2SCAN Meta-GGA                imeta=7
  !
  ! van der Waals functionals (nonlocal term only)
  !              "nonlc"  none                           inlc =0 (default)
  !--------------inlc = 1 to inlc = 25 reserved for vdW-DF--------------
  !              "vdw1"   vdW-DF1                        inlc =1
  !              "vdw2"   vdW-DF2                        inlc =2

  !              "w31c"   vdW-DF3-opt1                   inlc =3
  !              "w32c"   vdW-DF3-opt2                   inlc =4
  !              "wc6"    vdW-DF-C6                      inlc =5
  !---------------------------------------------------------------------
  !              "vv10"   rVV10                          inlc =26
  !
  ! Meta-GGA with van der Waals
  !              "rvv10-scan" rVV10 (with b=15.7) and scan inlc=26 (PRX 6, 041005 (2016))
  !
  ! Note: as a rule, all keywords should be unique, and should be different
  ! from the short name, but there are a few exceptions.
  !
  ! References:
  !              pz      J.P.Perdew and A.Zunger, PRB 23, 5048 (1981)
  !              vwn     S.H.Vosko, L.Wilk, M.Nusair, Can.J.Phys. 58,1200(1980)
  !              vwn1-rpa S.H.Vosko, L.Wilk, M.Nusair, Can.J.Phys. 58,1200(1980)
  !              wig     E.P.Wigner, Trans. Faraday Soc. 34, 67 (1938)
  !              hl      L.Hedin and B.I.Lundqvist, J. Phys. C4, 2064 (1971)
  !              gl      O.Gunnarsson and B.I.Lundqvist, PRB 13, 4274 (1976)
  !              pw      J.P.Perdew and Y.Wang, PRB 45, 13244 (1992)
  !              obpz    G.Ortiz and P.Ballone, PRB 50, 1391 (1994)
  !              obpw    as above
  !              b88     A.D.Becke, PRA 38, 3098 (1988)
  !              p86     J.P.Perdew, PRB 33, 8822 (1986)
  !              pw86    J.P.Perdew, PRB 33, 8800 (1986)
  !              b86b    A.D.Becke, J.Chem.Phys. 85, 7184 (1986)
  !              ob86    Klimes, Bowler, Michaelides, PRB 83, 195131 (2011)
  !              b86r    I. Hamada, Phys. Rev. B 89, 121103(R) (2014)
  !              w31x    D. Chakraborty, K. Berland, and T. Thonhauser, JCTC 16, 5893 (2020)
  !              w32x    D. Chakraborty, K. Berland, and T. Thonhauser, JCTC 16, 5893 (2020)
  !              pbe     J.P.Perdew, K.Burke, M.Ernzerhof, PRL 77, 3865 (1996)
  !              pw91    J.P.Perdew and Y. Wang, PRB 46, 6671 (1992)
  !              blyp    C.Lee, W.Yang, R.G.Parr, PRB 37, 785 (1988)
  !              hcth    Handy et al, JCP 109, 6264 (1998)
  !              olyp    Handy et al, JCP 116, 5411 (2002)
  !              revPBE  Zhang and Yang, PRL 80, 890 (1998)
  !              pbesol  J.P. Perdew et al., PRL 100, 136406 (2008)
  !              q2d     L. Chiodo et al., PRL 108, 126402 (2012)
  !              rw86    Eamonn D. Murray et al, J. Chem. Theory Comput. 5, 2754 (2009)
  !              wc      Z. Wu and R. E. Cohen, PRB 73, 235116 (2006)
  !              kzk     H.Kwee, S. Zhang, H. Krakauer, PRL 100, 126404 (2008)
  !              pbe0    J.P.Perdew, M. Ernzerhof, K.Burke, JCP 105, 9982 (1996)
  !              hse     Heyd, Scuseria, Ernzerhof, J. Chem. Phys. 118, 8207 (2003)
  !                      Heyd, Scuseria, Ernzerhof, J. Chem. Phys. 124, 219906 (2006).
  !              b3lyp   P.J. Stephens,F.J. Devlin,C.F. Chabalowski,M.J. Frisch
  !                      J.Phys.Chem 98, 11623 (1994)
  !              x3lyp   X. Xu, W.A Goddard III, PNAS 101, 2673 (2004)
  !              vdW-DF       M. Dion et al., PRL 92, 246401 (2004)
  !                           T. Thonhauser et al., PRL 115, 136402 (2015)
  !              vdW-DF2      Lee et al., Phys. Rev. B 82, 081101 (2010)
  !              rev-vdW-DF2  I. Hamada, Phys. Rev. B 89, 121103(R) (2014)
  !              vdW-DF-cx    K. Berland and P. Hyldgaard, PRB 89, 035412 (2014)
  !              vdW-DF-cx0   K. Berland, Y. Jiao, J.-H. Lee, T. Rangel, J. B. Neaton and P. Hyldgaard,
  !                           J. Chem. Phys. 146, 234106 (2017)
  !              vdW-DF-cx0p  Y. Jiao, E. Schröder and P. Hyldgaard,
  !                           J. Chem. Phys. 148, 194115 (2018)
  !              vdW-DF-obk8  Klimes et al, J. Phys. Cond. Matter, 22, 022201 (2010)
  !              vdW-DF-ob86  Klimes et al, Phys. Rev. B, 83, 195131 (2011)
  !              vdW-DF3-opt1 D. Chakraborty, K. Berland, and T. Thonhauser, JCTC 16, 5893 (2020)
  !              vdW-DF3-opt2 D. Chakraborty, K. Berland, and T. Thonhauser, JCTC 16, 5893 (2020)
  !              vdW-DF-C6    K. Berland, D. Chakraborty, and T. Thonhauser, PRB 99, 195418 (2019)
  !              c09x    V. R. Cooper, Phys. Rev. B 81, 161104(R) (2010)
  !              tpss    J.Tao, J.P.Perdew, V.N.Staroverov, G.E. Scuseria,
  !                      PRL 91, 146401 (2003)
  !              tb09    F Tran and P Blaha, Phys.Rev.Lett. 102, 226401 (2009)
  !              scan    J Sun, A Ruzsinszky and J Perdew, PRL 115, 36402 (2015)
  !              scan0   K Hui and J-D. Chai, JCP 144, 44114 (2016)
  !              r2scan  J. W. Furness, A. D. Kaplan, J. Ning, J. P. Perdew,
  !                      and J. Sun, JPCL 11, 8208 (2020)
  !              sogga   Y. Zhao and D. G. Truhlar, JCP 128, 184109 (2008)

  !              m06l    Y. Zhao and D. G. Truhlar, JCP 125, 194101 (2006)
  !              gau-pbe J.-W. Song, K. Yamashita, K. Hirao JCP 135, 071103 (2011)
  !              rVV10   R. Sabatini et al. Phys. Rev. B 87, 041108(R) (2013)
  !              ev93     Engel-Vosko, Phys. Rev. B 47, 13164 (1993)
  !              vdW-DF-ahcx V. Shukla, Y. Jiao, iC. M. Frostenson, and P. Hyldgaard, JPCM 34, 025902 (2022)
  !              vdW-DF2-ah V. Shukla, Y. Jiao, iC. M. Frostenson, and P. Hyldgaard, JPCM 34, 025902 (2022)
  !              PBE-ah V. Shukla, Y. Jiao, iC. M. Frostenson, and P. Hyldgaard, JPCM 34, 025902 (2022)
  !              PBESOL-ah V. Shukla, Y. Jiao, iC. M. Frostenson, and P. Hyldgaard, JPCM 34, 025902 (2022)
  !
  ! NOTE ABOUT HSE: there are two slight deviations with respect to the HSE06
  ! functional as it is in Gaussian code (that is considered as the reference
  ! in the chemistry community):
  ! - The range separation in Gaussian is precisely 0.11 bohr^-1,
  !   instead of 0.106 bohr^-1 in this implementation
  ! - The gradient scaling relation is a bit more complicated
  !   [ see: TM Henderson, AF Izmaylov, G Scalmani, and GE Scuseria,
  !          J. Chem. Phys. 131, 044108 (2009) ]
  ! These two modifications accounts only for a 1e-5 Ha difference for a
  ! single He atom. Info by Fabien Bruneval.
  !
  ! NOTE FOR LIBXC USERS: to use libxc functionals you must enforce them from input (use
  ! 'input_dft' in &system) and write their IDs in the input string. The only notation
  ! now allowed (v7.0) for input DFTs containing Libxc terms is:
  ! XC-000i-000i-000i-000i-000i-000i
  ! where you put the functional IDs instead of the zeros and an 'L' instead of
  ! 'i' if the functional is from Libxc. The order is the usual one:
  ! LDAexch - LDAcorr - GGAexch - GGAcorr - MGGAexch - MGGAcorr
  ! however QE will automatically adjust it if needed. You can skip zero tails (e.g.
  ! you don't need GGA/MGGA slots if the dft is LDA only and so on.
  ! You can use combinations of qe and libxc functionals, when they are compatible.
  ! You can also add vdW terms after it, for example, sla+pw+rw86+vdw2 is:
  ! input_dft='XC-001i-004i-013i-vdw2'.
  ! For more details see the user_guide (in 'Doc' folder).

Exact exchange (EXX)

See also

DFT functional (input_dft)

System
   ecutfock float
   ecutvcut float
   exxdiv_treatment [gygi-baldereschi | vcut_spherical | vcut_ws | none]
   exx_fraction float
   nqx1 integer
   nqx2 integer
   nqx3 integer
   screening_parameter float
   x_gamma_extrapolation Yes/No
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

ecutfock
Type:

Float

Unit:

Rydberg

GUI name:

Exchange operator cutoff

Description:

Kinetic energy cutoff for the exact exchange operator in EXX type calculations. By default this is the same as ecutrho but in some EXX calculations, a significant speed-up can be obtained by reducing ecutfock, at the expense of some loss in accuracy. Must be >= ecutwfc. Not implemented for stress calculation and for US-PP and PAW pseudopotentials. Use with care, especially in metals where it may give raise to instabilities.

ecutvcut
Type:

Float

Default value:

0.0

Unit:

Rydberg

Description:

Reciprocal space cutoff for correcting Coulomb potential divergencies at small q vectors.

exxdiv_treatment
Type:

Multiple Choice

Default value:

gygi-baldereschi

Options:

[gygi-baldereschi, vcut_spherical, vcut_ws, none]

GUI name:

Divergence treatment

Description:

Specific for EXX. It selects the kind of approach to be used for treating the Coulomb potential divergencies at small q vectors. gygi-baldereschi: appropriate for cubic and quasi-cubic supercells vcut_spherical: appropriate for cubic and quasi-cubic supercells vcut_ws: appropriate for strongly anisotropic supercells, see also ecutvcut. none: sets Coulomb potential at G,q=0 to 0.0 (required for GAU-PBE)

exx_fraction
Type:

Float

GUI name:

EXX fraction

Description:

Fraction of EXX for hybrid functional calculations. In the case of input_dft set to ‘PBE0’, the default value is 0.25, while for input_dft set to ‘B3LYP’ the exx_fraction default value is 0.20.

nqx1
Type:

Integer

Description:

Three-dimensional mesh for q (k1-k2) sampling of the Fock operator (EXX). Can be smaller than the number of k-points. Defaults to the size of the k-point mesh used.

nqx2
Type:

Integer

Description:

Three-dimensional mesh for q (k1-k2) sampling of the Fock operator (EXX). Can be smaller than the number of k-points. Defaults to the size of the k-point mesh used.

nqx3
Type:

Integer

Description:

Three-dimensional mesh for q (k1-k2) sampling of the Fock operator (EXX). Can be smaller than the number of k-points. Defaults to the size of the k-point mesh used.

screening_parameter
Type:

Float

Default value:

0.106

GUI name:

Screening parameter

Description:

screening_parameter for HSE like hybrid functionals. For more information, see: J. Chem. Phys. 118, 8207 (2003), doi:10.1063/1.1564060 J. Chem. Phys. 124, 219906 (2006), doi:10.1063/1.2204597

x_gamma_extrapolation
Type:

Bool

Default value:

Yes

GUI name:

Gamma extrapolation

Description:

Specific for EXX. If .true., extrapolate the G=0 term of the potential (see README in examples/EXX_example for more) Set this to .false. for GAU-PBE.

Dipole/charge corrections

See also

Control block: dipole/electric field

System
   edir [1 | 2 | 3]
   emaxpos float
   eopreg float
   eamp float
   assume_isolated [Auto | None | Martyna-Tuckerman | ESM | 2D]
End
System
Type:

Block

Description:

Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

edir
Type:

Multiple Choice

Options:

[1, 2, 3]

GUI name:

Field direction

Description:

The direction of the electric field or dipole correction is parallel to the bg(:,edir) reciprocal lattice vector. Thus the potential is constant in planes defined by FFT grid points. Used only if tefield is enabled.

emaxpos
Type:

Float

Default value:

0.5

GUI name:

Saw potential maximum

Description:

Position of the maximum of the saw-like potential along crystal axis edir, within the unit cell, see also eopreg. 0 < emaxpos < 1 Used only if tefield is enabled.

eopreg
Type:

Float

Default value:

0.1

GUI name:

Saw potential decreasing

Description:

Zone in the unit cell where the saw-like potential decreases, see also amp. Must be in range 0 < eopreg < 1. Used only if tefield is enabled.

eamp
Type:

Float

Default value:

0.001

Unit:

Hartree

GUI name:

Field amplitude

Description:

Amplitude of the electric field, in Hartree a.u. = = 51.4220632*10^10 V/m. Used only if tefield is enabled. The saw-like potential increases with slope eamp in the region from (emaxpos + eopreg- 1) to (emaxpos), then decreases to 0 until (emaxpos + eopreg), in units of the crystal vector edir. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result.

assume_isolated
Type:

Multiple Choice

Default value:

Auto

Options:

[Auto, None, Martyna-Tuckerman, ESM, 2D]

GUI name:

Isolated system

Description:

Used to perform calculation assuming the system to be isolated (a molecule or a cluster in a 3D supercell). Currently available choices: • Auto: determines the used method based on the periodicity of the system in the AMS driver input. None for systems 3D periodicity, Martyna-Tuckerman for systems without a lattice. • None: regular periodic calculation w/o any correction. • Martyna-Tuckerman: correction to both total energy and scf potential. Adapted from: G.J. Martyna, and M.E. Tuckerman, A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters, J. Chem. Phys. 110, 2810 (1999), [doi:10.1063/1.477923]. • ESM: Effective Screening Medium Method. For polarized or charged slab calculation, embeds the simulation cell within an effective semi-infinite medium in the perpendicular direction (along z). Embedding regions can be vacuum or semi-infinite metal electrodes (use esm_bc to choose boundary conditions). If between two electrodes, an optional electric field (esm_efield) may be applied. Method described in M. Otani and O. Sugino, ‘First-principles calculations of charged surfaces and interfaces: A plane-wave nonrepeated slab approach’, PRB 73, 115407 (2006). • 2D: Truncation of the Coulomb interaction in the z direction for structures periodic in the x-y plane. Total energy, forces and stresses are computed in a two-dimensional framework. Linear-response calculations () done on top of a self-consistent calculation with this flag will automatically be performed in the 2D framework as well. Please refer to: Sohier, T., Calandra, M., & Mauri, F. (2017), ‘Density functional perturbation theory for gated two-dimensional heterostructures: Theoretical developments and application to flexural phonons in graphene’, PRB, 96, 075448 (2017).

Hubbard U, DFT+U

Note: the Hubbard U (and J) settings are specified in the Quantum ESPRESSO 7.1 format (pdf).

This format is different compared to earlier versions of Quantum ESPRESSO. See the Examples for example usage in AMS.

Example: DFT+U (Dudarev’s formalism)

Hubbard ortho-atomic
    U Mn-3d 5.0   # eV
    U Ni-3d 6.0   # eV
End

Instead of 3d, you can also specify for example 4s etc.

To apply the Hund J0 (DFT+U+J0):

Hubbard ortho-atomic
    U  Mn-3d 5.0   # eV
    J0 Mn-3d 1.0   # eV
    U  Ni-3d 6.0   # eV
    J0 Ni-3d 1.2   # eV
End

Example: DFT+U+J (Liechtenstein’s formulation)

Hubbard ortho-atomic
    U Mn-3d 5.0
    J Mn-3d 1.0
    B Mn-3d 1.1
End

For details, see the Quantum ESPRESSO documentation for Hubbard U (pdf).

Hubbard
Type:

Non-standard block

Description:

Specify parameters for DFT+U models. The type of Hubbard projectors to use (e.g. atomic or ortho-atomic is specified in the header of this block. Example input: Hubbard ortho-atomic U Fe-3d 3.0 End More examples can be found in the documentation.

Properties:

Properties
   BandStructure Yes/No
   DOS Yes/No
   NormalModes Yes/No
   Phonons Yes/No
   WorkFunction Yes/No
End
Properties
Type:

Block

Description:

Configures which QE level properties to calculate for SinglePoint calculations or other important geometries (e.g. at the end of an optimization).

BandStructure
Type:

Bool

Default value:

No

GUI name:

Calculate band structure

Description:

If true, the band structure is calculated and saved for visualization. To configure the parameters of the calculation, please modify the options in the the section ‘BandStructure’.

DOS
Type:

Bool

Default value:

No

GUI name:

Calculate DOS

Description:

If true, the Density-Of-States (DOS) is calculated and saved for visualization. To configure the parameters of the calculation, please modify the options in the the section ‘DOS’.

NormalModes
Type:

Bool

Default value:

No

GUI name:

Frequencies

Description:

If true, frequencies and normal modes of vibration are calculated and saved for visualization. To configure the parameters of the calculation, please modify the options in the the section ‘NormalModes’.

Phonons
Type:

Bool

Default value:

No

GUI name:

Calculate Phonons

Description:

If true, the phonons are calculated and saved for visualization. To configure the parameters of the calculation, please modify the options in the the section ‘Phonons’.

WorkFunction
Type:

Bool

Default value:

No

GUI name:

Calculate work function

Description:

If true, the work function is calculated and saved for visualization. To configure the parameters of the calculation, please modify the options in the the section ‘WorkFunction’.

Density of states: DOS, PDOS

DOS
   DeltaE float
   Emax float
   Emin float
   K_Points header # Non-standard block. See details.
      ...
   End
   K_PointsStep float
   PDOS Yes/No
   degauss float
   nbnd integer
   ngauss [SimpleGaussian | Methfessel-Paxton | ColdSmearing | Fermi-Dirac | Default]
   occupations [Smearing | Tetrahedra | Tetrahedra_lin | Tetrahedra_opt | Fixed | Auto]
End
DOS
Type:

Block

Description:

This section configures the parameters for calculating the Density of States (DOS). These are the utilities involved: • kpath: This AMS tool generates an automated high-symmetry k-path in the Brillouin zone. • pw.x (with calculation=nscf): This Quantum ESPRESSO (QE) utility conducts electronic structure calculations, specifically for the non-self-consistent field (nscf) computation. • dos.x: A QE utility utilized for post-processing electronic structure calculations. It analyzes the electronic wavefunctions obtained from preceding calculations to determine the density of available electronic states at different energy levels. For more details see https://www.quantum-espresso.org/Doc/INPUT_DOS.html • projwfc.x: Another QE utility employed for post-processing electronic structure calculations. It projects the wavefunctions onto atomic orbitals or basis sets, offering insights into the composition and character of electronic states. For more details see https://www.quantum-espresso.org/Doc/INPUT_PROJWFC.html By default, the calculation sequence follows the order: kpath -> pw.x(calculation=nscf) -> dos.x. However, enabling DOS%PDOS switches the calculation to use projwfc.x instead of dos.x. While common parameters can be customized directly in this section, specialized adjustments should be made in either the DOS_X or PROJWFC_X section, depending on specific requirements.

DeltaE
Type:

Float

Default value:

0.1

Unit:

eV

GUI name:

Energy step

Description:

Energy grid step.

Emax
Type:

Float

Unit:

eV

Description:

Maximum energy for DOS plot. If unspecified, the upper band value, plus 3 times the value of the gaussian smearing if present, will be used.

Emin
Type:

Float

Unit:

eV

Description:

Minimum energy for DOS plot. If unspecified, the lower band value, minus 3 times the value of the gaussian smearing if present, will be used.

K_Points
Type:

Non-standard block

Description:

Specify the k-points to use. Choose a header appropriate for your system. Available values are: tpiba, automatic, crystal, gamma, tpiba_b, crystal_b, tpiba_c, crystal_c, and ams_kpath. See the QE documentation for details. If omitted, the k-points specified in the main QE calculation will be used. For most cases, automatic (which generates a Monkhorst-Pack grid) is recommended.

K_PointsStep
Type:

Float

Default value:

0.05

Unit:

1/Bohr

Description:

This option is used only if the header of the DOS%K_Points block is ams_kpath.

PDOS
Type:

Bool

Default value:

No

GUI name:

Calculate PDOS and Lowdin charges

Description:

If true, the partial Density-Of-States (projections on atomic basis functions) is calculated and saved for visualization. It uses the QE-utility projwfc.x. To configure the parameters of the calculation, please modify the options in the the section PROJWFC_X.

degauss
Type:

Float

Unit:

Rydberg

GUI name:

Broadening width

Description:

Gaussian broadening. See more details in sections DOS_X or PROJWFC_X.

nbnd
Type:

Integer

GUI name:

Number of bands

Description:

Number of electronic states (bands) to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled. Default: 20% more (minimum of 4 additional bands) than the number used in the main ‘pw.x’ calculation, regardless of the material’s insulating or metallic nature. Notice that this default is calculated differently than in standard QE.

ngauss
Type:

Multiple Choice

Default value:

Default

Options:

[SimpleGaussian, Methfessel-Paxton, ColdSmearing, Fermi-Dirac, Default]

GUI name:

Broadening type

Description:

Type of gaussian broadening: Available options are: • SimpleGaussian. • Methfessel-Paxton: Methfessel-Paxton of order 1. • ColdSmearing: Marzari-Vanderbilt-DeVita-Payne. • Fermi-Dirac: Fermi-Dirac function. • Default: See more details in sections DOS_X or PROJWFC_X.

occupations
Type:

Multiple Choice

Default value:

Auto

Options:

[Smearing, Tetrahedra, Tetrahedra_lin, Tetrahedra_opt, Fixed, Auto]

GUI name:

Non-SCF Occupations

Description:

Available options are: • Smearing: gaussian smearing for metals; see keywords smearing and degauss • Tetrahedra: Tetrahedron method, Bloechl’s version: P.E. Bloechl, PRB 49, 16223 (1994). Requires uniform grid of k-points, to be automatically generated (see block K_Points). Well suited for calculation of DOS, less so (because not variational) for force/optimization/dynamics calculations. • Tetrahedra_lin: Original linear tetrahedron method. To be used only as a reference; the optimized tetrahedron method is more efficient. • Tetrahedra_opt: optimized tetrahedron method, see M. Kawamura, PRB 89, 094515 (2014). Can be used for phonon calculations as well. • Fixed: for insulators with a gap. • Auto: Uses Tetrahedra for 3D and 2D systems, and Fixed for 0D and 1D systems.

Electronic band structure

Before calculating the band structure, make sure that the crystal unit cell corresponds to the primitive unit cell!

BandStructure
   K_Points header # Non-standard block. See details.
      ...
   End
   K_PointsLabels string
   K_PointsStep float
   UseSeeKPath Yes/No
   nbnd integer
End
BandStructure
Type:

Block

Description:

This section configures the parameters for calculating the Band Structure. This involves utilizing the following utilities in sequential order: • kpath: This AMS tool generates an automated high-symmetry k-path in the Brillouin zone. • pw.x (with calculation=bands): This utility from Quantum ESPRESSO (QE) performs electronic structure calculations, particularly for bands. For more details see https://www.quantum-espresso.org/Doc/INPUT_PW.html • bands.x: Another QE utility, which calculates the band structure. For more details see https://www.quantum-espresso.org/Doc/INPUT_BANDS.html.

K_Points
Type:

Non-standard block

Description:

Specify the k-points to use. Choose a header appropriate for your system. Available values are: tpiba, automatic, crystal, gamma, tpiba_b, crystal_b, tpiba_c, crystal_c, and ams_kpath. See the QE documentation for details. If omitted, ams_kpath will be used for 3D systems, and gamma otherwise. For most cases, ams_kpath (which generates a convenient path along high-symmetry k-points in the Brillouin zone) is recommended.

K_PointsLabels
Type:

String

Description:

You can provide labels for your k-points, like L-G-X-U-G, separating each label with a hyphen (-) or a vertical bar (|). For example, L-G-X-U-G and L|G|X|U|G are both valid. These labels are optional and only used for display purposes when the K_Points block is specified. This option is used only if the header of the BandStructure%K_Points block is ams_kpath. **Important:** These labels do not determine the actual k-point coordinates. You must specify the k-point coordinates separately within the K_Points section.

K_PointsStep
Type:

Float

Default value:

0.05

Unit:

1/Bohr

Description:

This option is used only if the header of the BandStructure%K_Points block is ams_kpath.

UseSeeKPath
Type:

Bool

Default value:

No

GUI name:

Use SeeK-path

Description:

This option determines how the path through the Brillouin zone is generated when Automatic mode is enabled. Choosing Yes utilizes the external utility **SeeKPath** to automatically generate the k-path, leveraging its robust algorithm for finding an appropriate path through the high-symmetry points. Choosing No uses our built-in **KPath** program to generate the k-path. Please note that using **SeeKPath** for k-path generation is currently an experimental feature. See https://github.com/giovannipizzi/seekpath and https://doi.org/10.1016/j.commatsci.2016.10.015 for details about SeeKPath.

nbnd
Type:

Integer

GUI name:

Number of bands

Description:

Number of electronic states (bands) to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled. Default: 20% more (minimum of 4 additional bands) than the number used in the main ‘pw.x’ calculation, regardless of the material’s insulating or metallic nature. Notice that this default is calculated differently than in standard QE.

Work function

WorkFunction
   centralize Yes/No
   idir [1 | 2 | 3]
   npt integer
End
WorkFunction
Type:

Block

Description:

This section configures the parameters for calculating the Work Function. This involves utilizing the following utilities in sequential order: • pp.x: Calculates the the electrostatic potential using the results from the last Quantum ESPRESSO calculation. • average.x: Performs planar and macroscopic averages of the electrostatic potential along a specified direction, which are crucial for determining the vacuum level and subsequently the work function.

centralize
Type:

Bool

Default value:

Yes

Description:

Translates the calculated electrostatic potential along the ‘idir’ coordinate, respecting periodic boundary conditions, so that the geometric center of the system is at the center of the coordinate.

idir
Type:

Multiple Choice

Default value:

3

Options:

[1, 2, 3]

Description:

1, 2 or 3. Planar average is done in the plane orthogonal to direction idir, as defined for the crystal cell. The idir parameter defaults to the value of System%edir if it’s set. Otherwise, idir is set to 3.

npt
Type:

Integer

Description:

Number of points used for the final interpolation of the planar and macroscopic averages of the electrostatic potential. This controls the resolution of the averaged potential data. If npt is less than or equal to N_idir (the number of FFT grid points along the specified direction), no interpolation is performed and the raw FFT data is used. The default value is 10 * N_idir, which typically provides sufficient resolution for accurate work function calculations.

Expert input for post-processing

DOS_X (dos.x)

Warning

Use the DOS_X input block only if you cannot achieve your goal using the DOS block.

Input options for the dos.x program.

PROJWFC_X (projwfc.x)

Input options for the projwfc.x program.

Differences between AMS and standalone QE

  1. AMS enforces scf_must_converge = .false.

  2. The default value for Electrons%mixing_beta is 0.3 (smaller than the pw.x default of 0.7), to make SCF convergence more reliable.

  3. The pseudopotentials are specified in the engine Pseudopotentials block. They will then be appended to the ATOMIC_SPECIES lines in the pw.x input.

  4. AMS automatically sets pseudo_dir, outdir, prefix, title, ntyp and nat

  5. AMS automatically generates a path through the Brillouin zone for band structure calculations by default

  6. For more differences, see the Quick reference (migration guide)